The present invention relates to a method for operating an internal-combustion engine and to an installation for performing the method.
German Published Patent Application No. 195 22 075 describes a method for forming a fuel/air mixture and a fuel feed installation for an internal-combustion engine, in which the fuel which is to be fed to the internal-combustion engine is vaporized and the fuel vapor which is generated is fed to the air which is sucked in by the internal-combustion engine. To reduce the emissions of hydrocarbons, the vaporization of the fuel is to be performed at relatively low temperatures.
However, a drawback of this method and the associated installation is the considerable additional outlay which is required for the vaporization of the fuel.
Since, in particular during and immediately after the cold-starting of an internal-combustion engine, there is as yet no or only an unsatisfactory conversion of the pollutants which are generated by the internal-combustion engine in a downstream catalytic converter, the exhaust emissions from the internal-combustion engine are very high in particular at this time. This fact is made even worse because, due to the poor preparation of the mixture in the cold state of the internal-combustion engine, the raw emissions themselves are particularly high, and because, in order to achieve more rapid heating of the catalytic converter, the mixture is additionally enriched, with the result that some unburnt fuel may leave the internal-combustion engine. However, it is precisely the emissions during a cold start which are the decisive factor in determining whether or not an internal-combustion engine is able to comply with a set exhaust restriction.
It is conventional to provide heated or air-surrounded injection valves or alternatively heating of the induction ports. However, practical implementation of these components either requires considerable outlay or means that their action is unsatisfactory with regard to reducing the exhaust emissions, in particular in the cold state of the internal-combustion engine.
Therefore, it is an object of the present invention to provide a method for operating an internal-combustion engine which, with the minimum possible outlay, enables emissions to be minimized during the starting operation and the warm-up phase of the internal-combustion engine.
The above and other beneficial objects of the present invention are achieved by providing a method and an arrangement as described herein.
According to the present invention, fuel in vapor form may be taken either from the fuel tank or from the charcoal canister, an operation which is very easy to control in terms of the process involved and only entails an extremely low outlay on the installation. Fuel in vapor form, which is naturally contained in the fuel tank or in the charcoal canister, does not have to be laboriously generated, but rather may very easily be removed from these containers in order to start and/or warm up the internal-combustion engine.
With regard to the preparation of the mixture and the resulting crude emissions from the internal-combustion engine, fuel which is in vapor form is much more suitable than liquid fuel, and consequently replacing at least some of the liquid fuel with fuel which is in vapor form, in accordance with the present invention, enables the emissions from the internal-combustion engine to be reduced considerably while the engine is starting and/or warming up.
Fuel may also be removed from the fuel tank or from the charcoal canister simultaneously or sequentially.
An arrangement configured to perform the method according to the present invention may require very few additional components.